LRP1 influences trafficking of N-type calcium channels via interaction with the auxiliary α2δ-1 subunit

Abstract

Voltage-gated Ca2+ (CaV) channels consist of a pore-forming α1 subunit, which determines the main functional and pharmacological attributes of the channel. The CaV1 and CaV2 channels are associated with auxiliary β- and α2δ-subunits. The molecular mechanisms involved in α2δ subunit trafficking, and the effect of α2δ subunits on trafficking calcium channel complexes remain poorly understood. Here we show that α2δ-1 is a ligand for the Low Density Lipoprotein (LDL) Receptor-related Protein-1 (LRP1), a multifunctional receptor which mediates trafficking of cargoes. This interaction with LRP1 is direct, and is modulated by the LRP chaperone, Receptor-Associated Protein (RAP). LRP1 regulates α2δ binding to gabapentin, and influences calcium channel trafficking and function. Whereas LRP1 alone reduces α2δ-1 trafficking to the cell-surface, the LRP1/RAP combination enhances mature glycosylation, proteolytic processing and cell-surface expression of α2δ-1, and also increase plasma-membrane expression and function of CaV2.2 when co-expressed with α2δ-1. Furthermore RAP alone produced a small increase in cell-surface expression of CaV2.2, α2δ-1 and the associated calcium currents. It is likely to be interacting with an endogenous member of the LDL receptor family to have these effects. Our findings now provide a key insight and new tools to investigate the trafficking of calcium channel α2δ subunits.

CaV2 channel subtype expression in rat sympathetic neurons is selectively regulated by α2δ subunits

“…For example, a 2 d-1 can serve as the receptor for thrombospodin, 34 a protein involved in developing synapses, or LRP-1 to influence Ca V channel trafficking. 35 It was also theorized that a 2 d-1 serves as an initial organizer for the synapse. 34 It may be possible then the Ca V 2.1 is selectively chosen for presynaptic expression in newly developed or developing synapses.…”

Analgesia with Gabapentin and Pregabalin May Involve N-Methyl-d-Aspartate Receptors, Neurexins, and Thrombospondins

“…However, two separate studies have failed to show that gabapentin directly disrupts the molecular interaction between thrombospondin and 2-1 proteins in vitro (Lana et al, 2016;El-Awaad et al, 2019), suggesting that the inhibition by gabapentin of thrombospondin actions could be indirect or require the presence of other proteins. Additional studies suggest that signaling proteins, including the scaffolding protein LRP1 (Kadurin et al, 2017) or activation of the small Rho GTPase, Ras-related C3 botulinum toxin substrate 1 (Rac1) are part of the biochemical pathway involved in the synaptogenic action that is inhibited by gabapentinoid drugs (Risher et al, 2018). Interestingly, LRP1 also was found to interact with 1-integrins at the cell surface to regulate their function (Theret et al, 2017).…”

“…Brain 2-1 also interacts directly with the membrane-bound protein trafficking molecule LRP1, a transmembrane protein that is involved in mediating 2-1 effects on calcium channel traffic to and from the membrane (Kadurin et al, 2017). LRP1 has many protein-interacting domains and is known to interact with a variety of other proteins (Lillis et al, 2008) NMDA receptors) and the endoplasmic reticulum protein calreticulin.…”

“…E. BK-type calcium dependent potassium channels (bright green) associate with 2-1 in a mutually exclusive manner with calcium channel 1 (Zhang et al, 2018) but effects of gabapentinoid drugs on BK channels (if any) are not known. F. LRP1 (lipoprotein related protein receptor 1, blue) binds to the 2-1 VWA domain via two extracellular ligand binding domains (Kadurin et al, 2017). Gabapentin interferes with the action of presynaptic NMDA receptors in several systems (Chen et al, 2018;Luo et al, 2018;Ma et al, 2018;Zhou et al, 2018;Chen et al, 2019;Deng et al, 2019) to reduce the spontaneous release of synaptic vesicles and decrease NMDA receptor function.…”

Different α2δ Accessory Subunits Regulate Distinctly Different Aspects of Calcium Channel Function in the Same Drosophila Neurons

“…Consequently, mutations in α 2 δ genes are cause to neurological conditions such as ataxia (Calandre et al, 2016;Davies et al, 2007;Klugbauer et al, 2003), epilepsy (Faria et al, 2017;Celli et al, 2017;Dolphin, 2012;2013), and neuropathic pain (Chen et al, 2019;Nieto-Rostro et al, 2018, Bauer et al, 2009). However, despite numerous reports on the roles of α 2 δ subunits in HVA channel trafficking (Kadurin et al, 2017;Hendrich et al, 2008), surfacing (D'Arco et al, 2015;Cassidy et al 2014), and biophysical properties (Savalli et al, 2016;Davies et al, 2010, Felix et al, 1997, Hobom et al, 2000, Cantí et al, 2005, the specific in vivo functions that may result from different α 2 δ/α 1 combinations remain incompletely understood. In heterologous expression systems, full calcium current amplitudes require co-expression of α 2 δ and β with the pore forming HVA VGCC α 1 subunit (Barclay et al, 2001;Brodbeck et al, 2002;Davies et al, 2006;Cantí et al, 2005;Hoppa et al, 2012; for review see Dolphin, 2013), largely independent of which α 2 δ subunit is used, indicating redundant functions of α 2 δ subunits.…”